1. Field of the Invention
This invention relates to a chemical analysis system for determining a concentration of a predetermined chemical component in a sample liquid such as blood, urine or the like spotted on a chemical analysis element and for determining an activity of a specific ion in a sample liquid such as blood, urine or the like spotted on a chemical analysis element and to a blood filtering unit for separating blood plasma, serum or the like from whole blood.
2. Description of the Related Art
There has been put into practice a dry ("dry-to-the-touch") chemical analysis element with which a specific chemical component or a solid component contained in a sample liquid can be quantitatively analyzed by only spotting a droplet of the sample liquid onto the element.
When quantitatively analyzing the chemical components or the like contained in a sample liquid using such a dry chemical analysis element, a droplet of the sample liquid is spotted onto the element and is held at a constant temperature for a predetermined time (incubation) in an incubator so that coloring reaction occurs, and the optical density of the color formed by the coloring reaction is optically measured. That is, measuring light containing a wavelength which is pre-selected according to the combination of the component to be analyzed and the reagent contained in the reagent layer of the element is projected onto the element and the optical density of the element is measured. Then the concentration of the component to be analyzed is determined on the basis of the optical density using a standard curve which represents the relation between the concentration of the biochemical component and the optical density.
In the chemical analysis system, the chemical analysis elements are transferred to the incubator one by one in sequence and taken out from the incubator to be discarded after measurement of the concentration. For example, as disclosed in Japanese Unexamined Patent Publication No. 61(1986)-26864, U.S. Pat. No. 4,296,069, the chemical analysis elements are carried in a disc-like incubator from the outer side of the incubator and taken out from the outer side of the same by ejecting the chemical analysis element from the inner side of the same or drawing out the chemical analysis element from the outer side of the incubator.
Further there has been known a chemical analysis system in which the incubator is rotatable about its axis and has a plurality of chemical analysis element receiving portions arranged in a circle about the axis of rotation of the incubator and each chemical analysis element is inserted into one of the receiving portions by a conveyor means which conveys the chemical analysis element linearly toward the axis of rotation of the incubator and is pushed further toward the axis of rotation of the incubator by the conveyor means, after measurement of the concentration, into a discarding hole which opens at the center of the incubator. (See Japanese Unexamined Patent Publication No. 6(1994)-66818.)
Further there has been known an ionic activity measuring system for measuring an activity of a specific ion contained in a sample liquid as disclosed, for instance, in U.S. Pat. No. 4,257,862, Japanese Patent Publication No. 58(1983)-4981, Japanese Unexamined Patent Publication Nos. 58(1983)-156848 and 58(1983)-211648 and Japanese Patent Publication No. 6(1994)-82113. A chemical analysis element used in such an ionic activity measuring system comprises a pair of ion selective electrodes and a porous bridge which connects the ion selective electrodes. When a reference liquid containing therein the specific ion whose ionic activity is known is spotted onto one of the ion selective electrodes and a sample liquid containing therein the specific ion whose ionic activity is not known is spotted onto the other ion selective electrode, the reference liquid and the sample liquid come to electrically contact with each other through the porous bridge and a potential difference is produced between the ion selective electrodes according to the difference in the ionic activity between the specific ions contained in the sample liquid and the reference liquid. The ionic activity of the specific ion in the sample liquid can be determined according to the potential difference on the basis of a standard curve which has been obtained in advance according to Nernst equation.
It is preferred that the ionic activity measuring system for measuring the ionic activity of a specific ion in a sample liquid using such a chemical analysis element be in the form of an analyzer which is provided with both function to spotting the sample liquid and the reference liquid onto the ion selective electrodes and function to measure the potential difference. In such an analyzer, the chemical analysis element spotted with the sample liquid and the reference liquid is transferred to a potential difference measuring section, where potential measurement probes are brought into contact with the ion selective electrodes to measure the potential difference between the electrodes.
Further when the biochemical component contained in blood is analyzed or the activity of a specific ion in blood is measured, generally blood plasma or serum is separated from the whole blood and the blood plasma or the serum separated from the whole blood is used as the sample liquid. Conventionally the blood plasma and the serum are separated from the whole blood by centrifuging. However centrifuging takes a long time and a lot of labor. Accordingly it is difficult to deal with an emergency. Further, when a plurality of samples are to be processed in a short time and/or the samples are to be processed on the spot, use of a motorized centrifugal separator is inconvenient. Accordingly, there have been a demand for a method of separating the plasma or serum by filtration.
There have proposed various methods of separating blood plasma in which whole blood is poured into a column filled with glass fiber filter paper and various microporous membranes such as of cellulose acetate from one end of the column and blood plasma is extracted from the other end of the column while increasing or reducing the pressure in the column. See, for instance, Japanese Patent Publication Nos. 44(1969)-14673 and 5(1993)-52463 and Japanese Unexamined Patent Publication Nos. 2(1990)-208565 and 4(1992)-208856.
However, at present, there has not been developed a method which can separate blood plasma or serum from whole blood in an amount necessary for measurement of the concentration of a specific component or measurement of the activity of a specific ion.
We have developed a blood filtering system which can efficiently separate blood plasma and/or serum from a fine amount of blood. In this blood filtering system, a combination of glass fiber filter paper and microporous membrane is employed as the filer medium and a seal member is provided on the plasma outlet side of the filter medium to reduce the opening area of the filter medium. See Japanese Patent Application No. 8(1996)-7692. Further in the blood filtering system disclosed in Japanese Patent Application No. 8(1996)-91621, a plasma receiving container is provided on the plasma outlet side of the filter medium.
However these blood filtering systems are disadvantageous in that since the whole blood is filtered by simply applying suction force to the whole blood, filtration takes a long time when the suction force is too weak while the components of the blood can be destroyed when the suction force is too strong.